linux-kernel - Re: n900 in next-20170901

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Message-ID: <20171114063724.GA16969@js1304-P5Q-DELUXE>
Date:   Tue, 14 Nov 2017 15:37:24 +0900
From:   Joonsoo Kim <iamjoonsoo.kim@....com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Pavel Machek <pavel@....cz>, pali.rohar@...il.com, sre@...nel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, khilman@...nel.org,
        aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
        patrikbachan@...il.com, serge@...lyn.com, abcloriens@...il.com,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Russell King <linux@...linux.org.uk>
Subject: Re: n900 in next-20170901

On Fri, Nov 10, 2017 at 07:36:20AM -0800, Tony Lindgren wrote:
> * Joonsoo Kim <iamjoonsoo.kim@....com> [171110 06:34]:
> > On Thu, Nov 09, 2017 at 07:26:10PM -0800, Tony Lindgren wrote:
> > > +#define OMAP34XX_SRAM_PHYS	0x40200000
> > > +#define OMAP34XX_SRAM_VIRT	0xd0010000
> > > +#define OMAP34XX_SRAM_SIZE	0x10000
> > 
> > For my testing environment, vmalloc address space is started at
> > roughly 0xe0000000 so 0xd0010000 would not be valid.
> 
> Well we can map it anywhere we want, got any preferences?

My testing environment is a beagle-(xm?) for QEMU. It is configured by
CONFIG_VMSPLIT_3G=y so kernel address space is started at 0xc0000000.
And, it has 512 MB memory so 0xc0000000 ~ 0xdff00000 is used for
direct mapping. See below.

[    0.000000] Memory: 429504K/522240K available (11264K kernel code,
1562K rwdata, 4288K rodata, 2048K init, 405K bss, 27200K reserved,
65536K cma-reserved, 0K highmem)
[    0.000000] Virtual kernel memory layout:
[    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)
[    0.000000]     fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)
[    0.000000]     vmalloc : 0xe0000000 - 0xff800000   ( 504 MB)
[    0.000000]     lowmem  : 0xc0000000 - 0xdff00000   ( 511 MB)
[    0.000000]     pkmap   : 0xbfe00000 - 0xc0000000   (   2 MB)
[    0.000000]     modules : 0xbf000000 - 0xbfe00000   (  14 MB)
[    0.000000]       .text : 0xc0208000 - 0xc0e00000   (12256 kB)
[    0.000000]       .init : 0xc1300000 - 0xc1500000   (2048 kB)
[    0.000000]       .data : 0xc1500000 - 0xc1686810   (1563 kB)
[    0.000000]        .bss : 0xc168fc68 - 0xc16f512c   ( 406 kB)

Therefore, if OMAP34XX_SRAM_VIRT is 0xd0010000, direct mapping is
broken and the system doesn't work. I guess that we should use more
stable address like as 0xf0000000.

> 
> Just that the current save_secure_ram_context uses "high_mask"
> of 0xffff to translate the address. To make this more flexible,
> we need the save_secure_ram_context changes too. So we might
> want to do the static mapping and save_secure_ram_context changes
> as a single patch.
> 
> > And, PHYS can be different according to the system type. Maybe either
> > OMAP3_SRAM_PUB_PA or OMAP3_SRAM_PA. It seems that SIZE and TYPE should
> > be considered, too. My understanding is correct?
> 
> We can have a static map for the whole SRAM area, see function
> __arm_ioremap_pfn_caller() for the comment "Try to reuse one of the
> static mapping whenever possible". So the different public SRAM start
> addresses and sizes don't matter there.

Okay. Look fine with SRAM start addresses and sizes. However, we need
to consider mtype since __arm_ioremap_pfn_caller() doesn't reuse the
mapping if mtype is different. mtype can be either MT_MEMORY_RWX or
MT_MEMORY_RWX_NONCACHED.

Thanks.